Conduct research for the control of lung cancer. Screen males over 45 years of age who smoke a pack or more a day of cigarettes derived from industrial groups and the general population. Tho thousand individuals will be entered in the test group, and 2,000 in a control group. These high-risk individuals offer the best possibility for evaluating: the efficacy of sputum cytopathology in detecting pulmonary neoplasms at an early state; the survival rate among screened cases compared with unscreened; and the efficacy of screening in reducing lung cancer mortality.